Popular smoking articles, such as cigarettes, have a substantially cylindrical rod shaped structure and include a charge, roll or column of smokable material such as shredded tobacco (e.g., in cut filler form) surrounded by a paper wrapper thereby forming a so-called “smokable rod” or “tobacco rod.” Normally, a cigarette has a cylindrical filter element aligned in an end-to-end relationship with the tobacco rod. Typically, a filter element comprises cellulose acetate tow plasticized using triacetin, and the tow is circumscribed by a paper material known as “plug wrap.” Typically, the filter element is attached to one end of the tobacco rod using a circumscribing wrapping material known as “tipping paper.” It also has become desirable to perforate the tipping material and plug wrap, in order to provide dilution of drawn mainstream smoke with ambient air. Descriptions of cigarettes and the various components thereof are set forth in Tobacco Production, Chemistry and Technology, Davis et al. (Eds.) (1999). A smoker employs a cigarette by lighting one end thereof and burning the tobacco rod. The smoker then receives mainstream smoke into his/her mouth by drawing on the opposite end (e.g., the filter end) of the cigarette.
Activated carbon particles or other adsorbent materials, such as silica gel, can be incorporated into a cigarette filter. Exemplary cigarettes and filters therefor are described in U.S. Pat. No. 3,353,543 to Sproull et al. and U.S. Pat. No. 4,481,958 to Ranier et al, and in PCT WO 02/37990 to Bereman. Certain commercially available filters have particles or granules of carbon (e.g., an activated carbon material or an activated charcoal material) dispersed within a fibrous material, such as described in U.S. Pat. No. 6,584,979 to Xue et al. Other commercially available filters have so-called “compartment filter” or “triple filter” designs, such as those filters described in U.S. Pat. No. 4,163,452 to Green et al.; U.S. Pat. No. 5,129,408 to Jakob et al.; and U.S. Pat. No. 6,537,186 to Veluz; as well as U.S. Patent Application Publication No. 2003/0106562. European Patent Application 0 579 410 A1 describes a filter including an annular section of carbon particles surrounding a cellulose acetate filter section. U.S. Pat. No. 5,360,023 to Blakley et al. describes a filter comprising a gathered paper that includes a carbonaceous material. Adsorbent materials incorporated into a cigarette filter can be used as a substrate for functional groups, such as described in U.S. Pat. No. 6,481,442 to Dyakonov et al. and U.S. Pat. No. 6,595,218 to Koller et al. Flavorants can be added to activated carbon as described in U.S. Patent Application Publication No. 2003/0159703. Exemplary commercially available filters are available as SCS IV Dual Solid Charcoal Filter from American Filtrona Corp.; Triple Solid Charcoal Filter from FIL International, Ltd.; Triple Compartment Filter from Baumgartner; and ACT from FIL International, Ltd.
Cigarette filter elements that incorporate carbon have a propensity to remove certain gas phase components from the mainstream smoke that passes through the filter element during draw by the smoker. Interaction of mainstream smoke with adsorbent substances, such as carbon particles, results in a certain degree of removal of certain gas phase compounds from the smoke. Such a change in the character of the smoke can result in changes in the sensory properties of the smoke. For example, mainstream tobacco smoke that is filtered using a conventional cigarette filter element incorporating carbon can often be characterized as having slightly metallic, drying and powdery flavor characteristics.
It would be desirable to provide a cigarette filter element that efficiently removes significant amounts of certain gas phase components of mainstream cigarette smoke. It would also be desirable to provide a cigarette filter that removes gas phase components of mainstream smoke while still yielding smoke with desirable sensory characteristics.